卡片视图未显示

Question

我正在尝试在Android Things开发人员工具包上的约束布局中显示卡片视图。 但是，我被困住了，不知道自己在做什么错。

也许与android的事物兼容性有关？

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:scaleType="centerCrop"
        android:src="@drawable/bg"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.0" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="20:30"
        android:textAlignment="center"
        android:textAppearance="@style/TextAppearance.AppCompat.Large"
        android:textColor="#FFFFFF"
        android:textSize="80sp"
        android:textStyle="bold"
        android:typeface="monospace"
        android:visibility="visible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />


    <androidx.cardview.widget.CardView
        android:id="@+id/card"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginBottom="@dimen/spacing_tiny"
        android:layout_marginLeft="@dimen/spacing_medium"
        android:layout_marginRight="@dimen/spacing_medium"
        android:layout_marginTop="@dimen/spacing_tiny"
        android:theme="@style/ThemeOverlay.AppCompat.Light"
        app:cardCornerRadius="4dp"
        app:cardElevation="1dp"
        app:cardUseCompatPadding="true"
        android:visibility="visible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="1.0">

        <LinearLayout
            android:id="@+id/linear"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical"
            android:paddingBottom="@dimen/spacing_small"
            android:paddingLeft="@dimen/spacing_medium"
            android:paddingRight="@dimen/spacing_medium"
            android:paddingTop="@dimen/spacing_small">

            <TextView
                android:id="@+id/status"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:text="@string/listening"
                android:textAppearance="@style/TextAppearance.AppCompat.Caption"
                android:textColor="@color/status_not_hearing"
                android:visibility="gone"
                tools:visibility="visible"/>

            <TextView
                android:id="@+id/text"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:paddingBottom="@dimen/spacing_small"
                android:paddingTop="@dimen/spacing_small"
                android:textAppearance="@style/TextAppearance.AppCompat.Large"
                tools:text="It is fine today."/>

        </LinearLayout>

    </androidx.cardview.widget.CardView>


</androidx.constraintlayout.widget.ConstraintLayout>

编辑器屏幕截图（外观）：

它的外观（卡片未显示其内容）：